I have an aerodynamic question relating to the negative pitch angle available on the tail rotor.
I have always assumed that the tail rotor would only ever require positive pitch to counteract the torque provided by the main rotor for pedal turns to the left (counter-clockwise rotating main rotor) and that turns to the right would only ever require
less positive pitch or even neutral pitch - but not negative pitch.
I cannot understand how the helicopter would ever be a situation that would require power to be
supplied the tail rotor for a right pedal turn - shouldn't the torque of the main rotor always provide enough yaw for this?
The only reason for negative pitch would be in an auto, when the torque of the main rotor is no longer an issue.
The following is a quote from the Rotocraft Flying Handbook:
The maximum positive pitch angle of the tail rotor is generally somewhat greater than the maximum negative pitch angle available. This is because the primary purpose of the tail rotor is to counteract the torque of the main rotor. The capability for tail rotors to produce thrust to the left (negative pitch angle) is necessary, because during autorotation the drag of the transmission tends to yaw the nose to the left, or in the same direction the main rotor is turning.
Now for the question. Are my assumptions correct or is there a situation in powered flight/hover that would require a negative pitch angle on the tail rotor?
Thanks for your input.
Jim.